Media captionThe BBC's Alastair Leithead was with government troops when they were ambushed

Sudan's President Omar al-Bashir has arrived in Juba for talks with South Sudanese President Salva Kiir over the conflict in South Sudan, reports say.

Separately, the two warring parties in South Sudan have begun direct talks in Ethiopia aiming at a ceasefire. No substantive progress has yet been made.

The conflict pits supporters of Mr Kiir against rebels led by his sacked deputy, Riek Machar.

At least 1,000 people have been killed since violence erupted on 15 December.

Analysis

By James CopnallSouth Sudan analyst

For the South Sudanese, President Omar al-Bashir has been the enemy for almost a quarter of a century. However, Khartoum's relationship with Juba has undoubtedly improved in the last few months.

Sudan's position is one of the big wild cards, but it may just be possible that both sides have concluded that the two Sudans can help each other, economically and politically, if they tone down the antagonism.

The Sudanese want the oil to keep flowing, as this brings in income to both Sudan and South Sudan.

In the past, during the north-south civil war that ultimately led to South Sudan's independence, Khartoum supported Riek Machar's forces when they split away from the mainstream rebel movement. Since this latest crisis began, Mr Bashir has certainly sounded supportive of President Salva Kiir. But everyone in South Sudan will be watching the Sudanese president closely.

The unrest started after Mr Kiir accused Mr Machar of attempting a coup - which he denies.

Nearly 200,000 people have been displaced in the conflict, which has taken on ethnic undertones. Mr Kiir is from the majority Dinka community and Mr Machar from the Nuer group.

'Peaceful resolution'

Mr Bashir says his visit to the South Sudanese capital Juba with a team of ministers is aimed at giving support for a regional initiative to solve the crisis.

"There should be peace and security in South Sudan," Mr Bashir said as he arrived in Juba.

"We come so that we can bring peace to South Sudan, to our brothers and sisters in South Sudan. Our relationship is very important," Mr Bashir said, according to AFP.

Sudan relies on revenue from oil transported through its southern neighbours' pipelines, which Khartoum fears will be disrupted by the fighting.

Meanwhile, East Africa's regional bloc the Intergovernmental Authority on Development (Igad) is trying to mediate between the South Sudanese government and its opponents at the talks in Ethiopia's capital, Addis Ababa.

China's Foreign Minister Wang Yi is also due to hold talks with the warring parties, in an attempt to push them to agree to a cessation of hostilities.

China is a major investor in South Sudan's oil industry.

Rebel negotiator Mabior Garang said he was optimistic about talks with the government, the AFP news agency reports.

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President Bashir arrived in Juba to lend his support for peace talks, state media said

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South Sudan gained independence from Sudan in 2011 after decades of conflict

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South Sudan's warring parties are negotiating in Ethiopia

However, he was "suspicious of the sincerity of the government" as it kept "shifting the goal posts", he said.

Up until Friday, the talks were conducted by mediators. Now, teams representing the opposing factions in South Sudan are expected to negotiate face to face.

Key issues are establishing a ceasefire, and the rebels' demand for the release of what they see as political prisoners.

Fresh fighting

Heavy fighting is continuing to the south of Bor, one of two cities held by rebels, says the BBC's Alastair Leithead, who was on the road between Juba and Bor.

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Nearly 200,000 people have been displaced in the conflict, which has taken on ethnic undertones

The rebels include a former military division made up of thousands of men who switched sides, our correspondent says.

Until a ceasefire is agreed, fighting is expected to continue or even intensify, he adds.

On Sunday, a South Sudanese army general was killed when a government convoy was ambushed.

South Sudan is the world's newest state. It was formed in 2011, gaining independence from Sudan after decades of conflict.

The latest trouble has its roots in tensions that go back long before 2011.

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Fighting erupted in the South Sudan capital, Juba, in mid-December. It followed a political power struggle between President Salva Kiir and his ex-deputy Riek Machar. The squabble has taken on an ethnic dimension as politicians' political bases are often ethnic.

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Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.

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Both Sudan and the South are reliant on oil revenue, which accounts for 98% of South Sudan's budget. They have fiercely disagreed over how to divide the oil wealth of the former united state - at one time production was shutdown for more than a year. Some 75% of the oil lies in the South but all the pipelines run north

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The two Sudans are very different geographically. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.

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After gaining independence in 2011, South Sudan is the world's newest country - and one of its poorest. Figures from 2010 show some 69% of households now have access to clean water - up from 48% in 2006. However, just 2% of households have water on the premises.

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Just 29% of children attend primary school in South Sudan - however this is also an improvement on the 16% recorded in 2006. About 32% of primary-age boys attend, while just 25% of girls do. Overall, 64% of children who begin primary school reach the last grade.

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Almost 28% of children under the age of five in South Sudan are moderately or severely underweight - this compares with the 33% recorded in 2006. Unity state has the highest proportion of children suffering malnourishment (46%), while Central Equatoria has the lowest (17%).